lib/lz4/lz4_decompress.c

   1 /*
   2  * LZ4 - Fast LZ compression algorithm
   3  * Copyright (C) 2011 - 2016, Yann Collet.
   4  * BSD 2 - Clause License (http://www.opensource.org/licenses/bsd - license.php)
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions are
   7  * met:
   8  *      * Redistributions of source code must retain the above copyright
   9  *        notice, this list of conditions and the following disclaimer.
  10  *      * Redistributions in binary form must reproduce the above
  11  * copyright notice, this list of conditions and the following disclaimer
  12  * in the documentation and/or other materials provided with the
  13  * distribution.
  14  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  15  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  16  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  17  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  18  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  19  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  20  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  24  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  25  * You can contact the author at :
  26  *      - LZ4 homepage : http://www.lz4.org
  27  *      - LZ4 source repository : https://github.com/lz4/lz4
  28  *
  29  *      Changed for kernel usage by:
  30  *      Sven Schmidt <[email protected]>
  31  */
  32
  33 /*-************************************
  34  *      Dependencies
  35  **************************************/
  36 #include "lz4defs.h"
  37 #include <linux/init.h>
  38 #include <linux/module.h>
  39 #include <linux/kernel.h>
  40 #include <linux/unaligned.h>
  41
  42 /*-*****************************
  43  *      Decompression functions
  44  *******************************/
  45
  46 #define DEBUGLOG(l, ...) {}     /* disabled */
  47
  48 #ifndef assert
  49 #define assert(condition) ((void)0)
  50 #endif
  51
  52 /*
  53  * LZ4_decompress_generic() :
  54  * This generic decompression function covers all use cases.
  55  * It shall be instantiated several times, using different sets of directives.
  56  * Note that it is important for performance that this function really get inlined,
  57  * in order to remove useless branches during compilation optimization.
  58  */
  59 static FORCE_INLINE int LZ4_decompress_generic(
  60          const char * const src,
  61          char * const dst,
  62          int srcSize,
  63                 /*
  64                  * If endOnInput == endOnInputSize,
  65                  * this value is `dstCapacity`
  66                  */
  67          int outputSize,
  68          /* endOnOutputSize, endOnInputSize */
  69          endCondition_directive endOnInput,
  70          /* full, partial */
  71          earlyEnd_directive partialDecoding,
  72          /* noDict, withPrefix64k, usingExtDict */
  73          dict_directive dict,
  74          /* always <= dst, == dst when no prefix */
  75          const BYTE * const lowPrefix,
  76          /* only if dict == usingExtDict */
  77          const BYTE * const dictStart,
  78          /* note : = 0 if noDict */
  79          const size_t dictSize
  80          )
  81 {
  82         const BYTE *ip = (const BYTE *) src;
  83         const BYTE * const iend = ip + srcSize;
  84
  85         BYTE *op = (BYTE *) dst;
  86         BYTE * const oend = op + outputSize;
  87         BYTE *cpy;
  88
  89         const BYTE * const dictEnd = (const BYTE *)dictStart + dictSize;
  90         static const unsigned int inc32table[8] = {0, 1, 2, 1, 0, 4, 4, 4};
  91         static const int dec64table[8] = {0, 0, 0, -1, -4, 1, 2, 3};
  92
  93         const int safeDecode = (endOnInput == endOnInputSize);
  94         const int checkOffset = ((safeDecode) && (dictSize < (int)(64 * KB)));
  95
  96         /* Set up the "end" pointers for the shortcut. */
  97         const BYTE *const shortiend = iend -
  98                 (endOnInput ? 14 : 8) /*maxLL*/ - 2 /*offset*/;
  99         const BYTE *const shortoend = oend -
 100                 (endOnInput ? 14 : 8) /*maxLL*/ - 18 /*maxML*/;
 101
 102         DEBUGLOG(5, "%s (srcSize:%i, dstSize:%i)", __func__,
 103                  srcSize, outputSize);
 104
 105         /* Special cases */
 106         assert(lowPrefix <= op);
 107         assert(src != NULL);
 108
 109         /* Empty output buffer */
 110         if ((endOnInput) && (unlikely(outputSize == 0)))
 111                 return ((srcSize == 1) && (*ip == 0)) ? 0 : -1;
 112
 113         if ((!endOnInput) && (unlikely(outputSize == 0)))
 114                 return (*ip == 0 ? 1 : -1);
 115
 116         if ((endOnInput) && unlikely(srcSize == 0))
 117                 return -1;
 118
 119         /* Main Loop : decode sequences */
 120         while (1) {
 121                 size_t length;
 122                 const BYTE *match;
 123                 size_t offset;
 124
 125                 /* get literal length */
 126                 unsigned int const token = *ip++;
 127                 length = token>>ML_BITS;
 128
 129                 /* ip < iend before the increment */
 130                 assert(!endOnInput || ip <= iend);
 131
 132                 /*
 133                  * A two-stage shortcut for the most common case:
 134                  * 1) If the literal length is 0..14, and there is enough
 135                  * space, enter the shortcut and copy 16 bytes on behalf
 136                  * of the literals (in the fast mode, only 8 bytes can be
 137                  * safely copied this way).
 138                  * 2) Further if the match length is 4..18, copy 18 bytes
 139                  * in a similar manner; but we ensure that there's enough
 140                  * space in the output for those 18 bytes earlier, upon
 141                  * entering the shortcut (in other words, there is a
 142                  * combined check for both stages).
 143                  *
 144                  * The & in the likely() below is intentionally not && so that
 145                  * some compilers can produce better parallelized runtime code
 146                  */
 147                 if ((endOnInput ? length != RUN_MASK : length <= 8)
 148                    /*
 149                     * strictly "less than" on input, to re-enter
 150                     * the loop with at least one byte
 151                     */
 152                    && likely((endOnInput ? ip < shortiend : 1) &
 153                              (op <= shortoend))) {
 154                         /* Copy the literals */
 155                         LZ4_memcpy(op, ip, endOnInput ? 16 : 8);
 156                         op += length; ip += length;
 157
 158                         /*
 159                          * The second stage:
 160                          * prepare for match copying, decode full info.
 161                          * If it doesn't work out, the info won't be wasted.
 162                          */
 163                         length = token & ML_MASK; /* match length */
 164                         offset = LZ4_readLE16(ip);
 165                         ip += 2;
 166                         match = op - offset;
 167                         assert(match <= op); /* check overflow */
 168
 169                         /* Do not deal with overlapping matches. */
 170                         if ((length != ML_MASK) &&
 171                             (offset >= 8) &&
 172                             (dict == withPrefix64k || match >= lowPrefix)) {
 173                                 /* Copy the match. */
 174                                 LZ4_memcpy(op + 0, match + 0, 8);
 175                                 LZ4_memcpy(op + 8, match + 8, 8);
 176                                 LZ4_memcpy(op + 16, match + 16, 2);
 177                                 op += length + MINMATCH;
 178                                 /* Both stages worked, load the next token. */
 179                                 continue;
 180                         }
 181
 182                         /*
 183                          * The second stage didn't work out, but the info
 184                          * is ready. Propel it right to the point of match
 185                          * copying.
 186                          */
 187                         goto _copy_match;
 188                 }
 189
 190                 /* decode literal length */
 191                 if (length == RUN_MASK) {
 192                         unsigned int s;
 193
 194                         if (unlikely(endOnInput ? ip >= iend - RUN_MASK : 0)) {
 195                                 /* overflow detection */
 196                                 goto _output_error;
 197                         }
 198                         do {
 199                                 s = *ip++;
 200                                 length += s;
 201                         } while (likely(endOnInput
 202                                 ? ip < iend - RUN_MASK
 203                                 : 1) & (s == 255));
 204
 205                         if ((safeDecode)
 206                             && unlikely((uptrval)(op) +
 207                                         length < (uptrval)(op))) {
 208                                 /* overflow detection */
 209                                 goto _output_error;
 210                         }
 211                         if ((safeDecode)
 212                             && unlikely((uptrval)(ip) +
 213                                         length < (uptrval)(ip))) {
 214                                 /* overflow detection */
 215                                 goto _output_error;
 216                         }
 217                 }
 218
 219                 /* copy literals */
 220                 cpy = op + length;
 221                 LZ4_STATIC_ASSERT(MFLIMIT >= WILDCOPYLENGTH);
 222
 223                 if (((endOnInput) && ((cpy > oend - MFLIMIT)
 224                         || (ip + length > iend - (2 + 1 + LASTLITERALS))))
 225                         || ((!endOnInput) && (cpy > oend - WILDCOPYLENGTH))) {
 226                         if (partialDecoding) {
 227                                 if (cpy > oend) {
 228                                         /*
 229                                          * Partial decoding :
 230                                          * stop in the middle of literal segment
 231                                          */
 232                                         cpy = oend;
 233                                         length = oend - op;
 234                                 }
 235                                 if ((endOnInput)
 236                                         && (ip + length > iend)) {
 237                                         /*
 238                                          * Error :
 239                                          * read attempt beyond
 240                                          * end of input buffer
 241                                          */
 242                                         goto _output_error;
 243                                 }
 244                         } else {
 245                                 if ((!endOnInput)
 246                                         && (cpy != oend)) {
 247                                         /*
 248                                          * Error :
 249                                          * block decoding must
 250                                          * stop exactly there
 251                                          */
 252                                         goto _output_error;
 253                                 }
 254                                 if ((endOnInput)
 255                                         && ((ip + length != iend)
 256                                         || (cpy > oend))) {
 257                                         /*
 258                                          * Error :
 259                                          * input must be consumed
 260                                          */
 261                                         goto _output_error;
 262                                 }
 263                         }
 264
 265                         /*
 266                          * supports overlapping memory regions; only matters
 267                          * for in-place decompression scenarios
 268                          */
 269                         LZ4_memmove(op, ip, length);
 270                         ip += length;
 271                         op += length;
 272
 273                         /* Necessarily EOF when !partialDecoding.
 274                          * When partialDecoding, it is EOF if we've either
 275                          * filled the output buffer or
 276                          * can't proceed with reading an offset for following match.
 277                          */
 278                         if (!partialDecoding || (cpy == oend) || (ip >= (iend - 2)))
 279                                 break;
 280                 } else {
 281                         /* may overwrite up to WILDCOPYLENGTH beyond cpy */
 282                         LZ4_wildCopy(op, ip, cpy);
 283                         ip += length;
 284                         op = cpy;
 285                 }
 286
 287                 /* get offset */
 288                 offset = LZ4_readLE16(ip);
 289                 ip += 2;
 290                 match = op - offset;
 291
 292                 /* get matchlength */
 293                 length = token & ML_MASK;
 294
 295 _copy_match:
 296                 if ((checkOffset) && (unlikely(match + dictSize < lowPrefix))) {
 297                         /* Error : offset outside buffers */
 298                         goto _output_error;
 299                 }
 300
 301                 /* costs ~1%; silence an msan warning when offset == 0 */
 302                 /*
 303                  * note : when partialDecoding, there is no guarantee that
 304                  * at least 4 bytes remain available in output buffer
 305                  */
 306                 if (!partialDecoding) {
 307                         assert(oend > op);
 308                         assert(oend - op >= 4);
 309
 310                         LZ4_write32(op, (U32)offset);
 311                 }
 312
 313                 if (length == ML_MASK) {
 314                         unsigned int s;
 315
 316                         do {
 317                                 s = *ip++;
 318
 319                                 if ((endOnInput) && (ip > iend - LASTLITERALS))
 320                                         goto _output_error;
 321
 322                                 length += s;
 323                         } while (s == 255);
 324
 325                         if ((safeDecode)
 326                                 && unlikely(
 327                                         (uptrval)(op) + length < (uptrval)op)) {
 328                                 /* overflow detection */
 329                                 goto _output_error;
 330                         }
 331                 }
 332
 333                 length += MINMATCH;
 334
 335                 /* match starting within external dictionary */
 336                 if ((dict == usingExtDict) && (match < lowPrefix)) {
 337                         if (unlikely(op + length > oend - LASTLITERALS)) {
 338                                 /* doesn't respect parsing restriction */
 339                                 if (!partialDecoding)
 340                                         goto _output_error;
 341                                 length = min(length, (size_t)(oend - op));
 342                         }
 343
 344                         if (length <= (size_t)(lowPrefix - match)) {
 345                                 /*
 346                                  * match fits entirely within external
 347                                  * dictionary : just copy
 348                                  */
 349                                 memmove(op, dictEnd - (lowPrefix - match),
 350                                         length);
 351                                 op += length;
 352                         } else {
 353                                 /*
 354                                  * match stretches into both external
 355                                  * dictionary and current block
 356                                  */
 357                                 size_t const copySize = (size_t)(lowPrefix - match);
 358                                 size_t const restSize = length - copySize;
 359
 360                                 LZ4_memcpy(op, dictEnd - copySize, copySize);
 361                                 op += copySize;
 362                                 if (restSize > (size_t)(op - lowPrefix)) {
 363                                         /* overlap copy */
 364                                         BYTE * const endOfMatch = op + restSize;
 365                                         const BYTE *copyFrom = lowPrefix;
 366
 367                                         while (op < endOfMatch)
 368                                                 *op++ = *copyFrom++;
 369                                 } else {
 370                                         LZ4_memcpy(op, lowPrefix, restSize);
 371                                         op += restSize;
 372                                 }
 373                         }
 374                         continue;
 375                 }
 376
 377                 /* copy match within block */
 378                 cpy = op + length;
 379
 380                 /*
 381                  * partialDecoding :
 382                  * may not respect endBlock parsing restrictions
 383                  */
 384                 assert(op <= oend);
 385                 if (partialDecoding &&
 386                     (cpy > oend - MATCH_SAFEGUARD_DISTANCE)) {
 387                         size_t const mlen = min(length, (size_t)(oend - op));
 388                         const BYTE * const matchEnd = match + mlen;
 389                         BYTE * const copyEnd = op + mlen;
 390
 391                         if (matchEnd > op) {
 392                                 /* overlap copy */
 393                                 while (op < copyEnd)
 394                                         *op++ = *match++;
 395                         } else {
 396                                 LZ4_memcpy(op, match, mlen);
 397                         }
 398                         op = copyEnd;
 399                         if (op == oend)
 400                                 break;
 401                         continue;
 402                 }
 403
 404                 if (unlikely(offset < 8)) {
 405                         op[0] = match[0];
 406                         op[1] = match[1];
 407                         op[2] = match[2];
 408                         op[3] = match[3];
 409                         match += inc32table[offset];
 410                         LZ4_memcpy(op + 4, match, 4);
 411                         match -= dec64table[offset];
 412                 } else {
 413                         LZ4_copy8(op, match);
 414                         match += 8;
 415                 }
 416
 417                 op += 8;
 418
 419                 if (unlikely(cpy > oend - MATCH_SAFEGUARD_DISTANCE)) {
 420                         BYTE * const oCopyLimit = oend - (WILDCOPYLENGTH - 1);
 421
 422                         if (cpy > oend - LASTLITERALS) {
 423                                 /*
 424                                  * Error : last LASTLITERALS bytes
 425                                  * must be literals (uncompressed)
 426                                  */
 427                                 goto _output_error;
 428                         }
 429
 430                         if (op < oCopyLimit) {
 431                                 LZ4_wildCopy(op, match, oCopyLimit);
 432                                 match += oCopyLimit - op;
 433                                 op = oCopyLimit;
 434                         }
 435                         while (op < cpy)
 436                                 *op++ = *match++;
 437                 } else {
 438                         LZ4_copy8(op, match);
 439                         if (length > 16)
 440                                 LZ4_wildCopy(op + 8, match + 8, cpy);
 441                 }
 442                 op = cpy; /* wildcopy correction */
 443         }
 444
 445         /* end of decoding */
 446         if (endOnInput) {
 447                 /* Nb of output bytes decoded */
 448                 return (int) (((char *)op) - dst);
 449         } else {
 450                 /* Nb of input bytes read */
 451                 return (int) (((const char *)ip) - src);
 452         }
 453
 454         /* Overflow error detected */
 455 _output_error:
 456         return (int) (-(((const char *)ip) - src)) - 1;
 457 }
 458
 459 int LZ4_decompress_safe(const char *source, char *dest,
 460         int compressedSize, int maxDecompressedSize)
 461 {
 462         return LZ4_decompress_generic(source, dest,
 463                                       compressedSize, maxDecompressedSize,
 464                                       endOnInputSize, decode_full_block,
 465                                       noDict, (BYTE *)dest, NULL, 0);
 466 }
 467
 468 int LZ4_decompress_safe_partial(const char *src, char *dst,
 469         int compressedSize, int targetOutputSize, int dstCapacity)
 470 {
 471         dstCapacity = min(targetOutputSize, dstCapacity);
 472         return LZ4_decompress_generic(src, dst, compressedSize, dstCapacity,
 473                                       endOnInputSize, partial_decode,
 474                                       noDict, (BYTE *)dst, NULL, 0);
 475 }
 476
 477 int LZ4_decompress_fast(const char *source, char *dest, int originalSize)
 478 {
 479         return LZ4_decompress_generic(source, dest, 0, originalSize,
 480                                       endOnOutputSize, decode_full_block,
 481                                       withPrefix64k,
 482                                       (BYTE *)dest - 64 * KB, NULL, 0);
 483 }
 484
 485 /* ===== Instantiate a few more decoding cases, used more than once. ===== */
 486
 487 static int LZ4_decompress_safe_withPrefix64k(const char *source, char *dest,
 488                                       int compressedSize, int maxOutputSize)
 489 {
 490         return LZ4_decompress_generic(source, dest,
 491                                       compressedSize, maxOutputSize,
 492                                       endOnInputSize, decode_full_block,
 493                                       withPrefix64k,
 494                                       (BYTE *)dest - 64 * KB, NULL, 0);
 495 }
 496
 497 static int LZ4_decompress_safe_withSmallPrefix(const char *source, char *dest,
 498                                                int compressedSize,
 499                                                int maxOutputSize,
 500                                                size_t prefixSize)
 501 {
 502         return LZ4_decompress_generic(source, dest,
 503                                       compressedSize, maxOutputSize,
 504                                       endOnInputSize, decode_full_block,
 505                                       noDict,
 506                                       (BYTE *)dest - prefixSize, NULL, 0);
 507 }
 508
 509 static int LZ4_decompress_safe_forceExtDict(const char *source, char *dest,
 510                                             int compressedSize, int maxOutputSize,
 511                                             const void *dictStart, size_t dictSize)
 512 {
 513         return LZ4_decompress_generic(source, dest,
 514                                       compressedSize, maxOutputSize,
 515                                       endOnInputSize, decode_full_block,
 516                                       usingExtDict, (BYTE *)dest,
 517                                       (const BYTE *)dictStart, dictSize);
 518 }
 519
 520 static int LZ4_decompress_fast_extDict(const char *source, char *dest,
 521                                        int originalSize,
 522                                        const void *dictStart, size_t dictSize)
 523 {
 524         return LZ4_decompress_generic(source, dest,
 525                                       0, originalSize,
 526                                       endOnOutputSize, decode_full_block,
 527                                       usingExtDict, (BYTE *)dest,
 528                                       (const BYTE *)dictStart, dictSize);
 529 }
 530
 531 /*
 532  * The "double dictionary" mode, for use with e.g. ring buffers: the first part
 533  * of the dictionary is passed as prefix, and the second via dictStart + dictSize.
 534  * These routines are used only once, in LZ4_decompress_*_continue().
 535  */
 536 static FORCE_INLINE
 537 int LZ4_decompress_safe_doubleDict(const char *source, char *dest,
 538                                    int compressedSize, int maxOutputSize,
 539                                    size_t prefixSize,
 540                                    const void *dictStart, size_t dictSize)
 541 {
 542         return LZ4_decompress_generic(source, dest,
 543                                       compressedSize, maxOutputSize,
 544                                       endOnInputSize, decode_full_block,
 545                                       usingExtDict, (BYTE *)dest - prefixSize,
 546                                       (const BYTE *)dictStart, dictSize);
 547 }
 548
 549 static FORCE_INLINE
 550 int LZ4_decompress_fast_doubleDict(const char *source, char *dest,
 551                                    int originalSize, size_t prefixSize,
 552                                    const void *dictStart, size_t dictSize)
 553 {
 554         return LZ4_decompress_generic(source, dest,
 555                                       0, originalSize,
 556                                       endOnOutputSize, decode_full_block,
 557                                       usingExtDict, (BYTE *)dest - prefixSize,
 558                                       (const BYTE *)dictStart, dictSize);
 559 }
 560
 561 /* ===== streaming decompression functions ===== */
 562
 563 int LZ4_setStreamDecode(LZ4_streamDecode_t *LZ4_streamDecode,
 564         const char *dictionary, int dictSize)
 565 {
 566         LZ4_streamDecode_t_internal *lz4sd =
 567                 &LZ4_streamDecode->internal_donotuse;
 568
 569         lz4sd->prefixSize = (size_t) dictSize;
 570         lz4sd->prefixEnd = (const BYTE *) dictionary + dictSize;
 571         lz4sd->externalDict = NULL;
 572         lz4sd->extDictSize      = 0;
 573         return 1;
 574 }
 575
 576 /*
 577  * *_continue() :
 578  * These decoding functions allow decompression of multiple blocks
 579  * in "streaming" mode.
 580  * Previously decoded blocks must still be available at the memory
 581  * position where they were decoded.
 582  * If it's not possible, save the relevant part of
 583  * decoded data into a safe buffer,
 584  * and indicate where it stands using LZ4_setStreamDecode()
 585  */
 586 int LZ4_decompress_safe_continue(LZ4_streamDecode_t *LZ4_streamDecode,
 587         const char *source, char *dest, int compressedSize, int maxOutputSize)
 588 {
 589         LZ4_streamDecode_t_internal *lz4sd =
 590                 &LZ4_streamDecode->internal_donotuse;
 591         int result;
 592
 593         if (lz4sd->prefixSize == 0) {
 594                 /* The first call, no dictionary yet. */
 595                 assert(lz4sd->extDictSize == 0);
 596                 result = LZ4_decompress_safe(source, dest,
 597                         compressedSize, maxOutputSize);
 598                 if (result <= 0)
 599                         return result;
 600                 lz4sd->prefixSize = result;
 601                 lz4sd->prefixEnd = (BYTE *)dest + result;
 602         } else if (lz4sd->prefixEnd == (BYTE *)dest) {
 603                 /* They're rolling the current segment. */
 604                 if (lz4sd->prefixSize >= 64 * KB - 1)
 605                         result = LZ4_decompress_safe_withPrefix64k(source, dest,
 606                                 compressedSize, maxOutputSize);
 607                 else if (lz4sd->extDictSize == 0)
 608                         result = LZ4_decompress_safe_withSmallPrefix(source,
 609                                 dest, compressedSize, maxOutputSize,
 610                                 lz4sd->prefixSize);
 611                 else
 612                         result = LZ4_decompress_safe_doubleDict(source, dest,
 613                                 compressedSize, maxOutputSize,
 614                                 lz4sd->prefixSize,
 615                                 lz4sd->externalDict, lz4sd->extDictSize);
 616                 if (result <= 0)
 617                         return result;
 618                 lz4sd->prefixSize += result;
 619                 lz4sd->prefixEnd  += result;
 620         } else {
 621                 /*
 622                  * The buffer wraps around, or they're
 623                  * switching to another buffer.
 624                  */
 625                 lz4sd->extDictSize = lz4sd->prefixSize;
 626                 lz4sd->externalDict = lz4sd->prefixEnd - lz4sd->extDictSize;
 627                 result = LZ4_decompress_safe_forceExtDict(source, dest,
 628                         compressedSize, maxOutputSize,
 629                         lz4sd->externalDict, lz4sd->extDictSize);
 630                 if (result <= 0)
 631                         return result;
 632                 lz4sd->prefixSize = result;
 633                 lz4sd->prefixEnd  = (BYTE *)dest + result;
 634         }
 635
 636         return result;
 637 }
 638
 639 int LZ4_decompress_fast_continue(LZ4_streamDecode_t *LZ4_streamDecode,
 640         const char *source, char *dest, int originalSize)
 641 {
 642         LZ4_streamDecode_t_internal *lz4sd = &LZ4_streamDecode->internal_donotuse;
 643         int result;
 644
 645         if (lz4sd->prefixSize == 0) {
 646                 assert(lz4sd->extDictSize == 0);
 647                 result = LZ4_decompress_fast(source, dest, originalSize);
 648                 if (result <= 0)
 649                         return result;
 650                 lz4sd->prefixSize = originalSize;
 651                 lz4sd->prefixEnd = (BYTE *)dest + originalSize;
 652         } else if (lz4sd->prefixEnd == (BYTE *)dest) {
 653                 if (lz4sd->prefixSize >= 64 * KB - 1 ||
 654                     lz4sd->extDictSize == 0)
 655                         result = LZ4_decompress_fast(source, dest,
 656                                                      originalSize);
 657                 else
 658                         result = LZ4_decompress_fast_doubleDict(source, dest,
 659                                 originalSize, lz4sd->prefixSize,
 660                                 lz4sd->externalDict, lz4sd->extDictSize);
 661                 if (result <= 0)
 662                         return result;
 663                 lz4sd->prefixSize += originalSize;
 664                 lz4sd->prefixEnd  += originalSize;
 665         } else {
 666                 lz4sd->extDictSize = lz4sd->prefixSize;
 667                 lz4sd->externalDict = lz4sd->prefixEnd - lz4sd->extDictSize;
 668                 result = LZ4_decompress_fast_extDict(source, dest,
 669                         originalSize, lz4sd->externalDict, lz4sd->extDictSize);
 670                 if (result <= 0)
 671                         return result;
 672                 lz4sd->prefixSize = originalSize;
 673                 lz4sd->prefixEnd = (BYTE *)dest + originalSize;
 674         }
 675         return result;
 676 }
 677
 678 int LZ4_decompress_safe_usingDict(const char *source, char *dest,
 679                                   int compressedSize, int maxOutputSize,
 680                                   const char *dictStart, int dictSize)
 681 {
 682         if (dictSize == 0)
 683                 return LZ4_decompress_safe(source, dest,
 684                                            compressedSize, maxOutputSize);
 685         if (dictStart+dictSize == dest) {
 686                 if (dictSize >= 64 * KB - 1)
 687                         return LZ4_decompress_safe_withPrefix64k(source, dest,
 688                                 compressedSize, maxOutputSize);
 689                 return LZ4_decompress_safe_withSmallPrefix(source, dest,
 690                         compressedSize, maxOutputSize, dictSize);
 691         }
 692         return LZ4_decompress_safe_forceExtDict(source, dest,
 693                 compressedSize, maxOutputSize, dictStart, dictSize);
 694 }
 695
 696 int LZ4_decompress_fast_usingDict(const char *source, char *dest,
 697                                   int originalSize,
 698                                   const char *dictStart, int dictSize)
 699 {
 700         if (dictSize == 0 || dictStart + dictSize == dest)
 701                 return LZ4_decompress_fast(source, dest, originalSize);
 702
 703         return LZ4_decompress_fast_extDict(source, dest, originalSize,
 704                 dictStart, dictSize);
 705 }
 706
 707 #ifndef STATIC
 708 EXPORT_SYMBOL(LZ4_decompress_safe);
 709 EXPORT_SYMBOL(LZ4_decompress_safe_partial);
 710 EXPORT_SYMBOL(LZ4_decompress_fast);
 711 EXPORT_SYMBOL(LZ4_setStreamDecode);
 712 EXPORT_SYMBOL(LZ4_decompress_safe_continue);
 713 EXPORT_SYMBOL(LZ4_decompress_fast_continue);
 714 EXPORT_SYMBOL(LZ4_decompress_safe_usingDict);
 715 EXPORT_SYMBOL(LZ4_decompress_fast_usingDict);
 716
 717 MODULE_LICENSE("Dual BSD/GPL");
 718 MODULE_DESCRIPTION("LZ4 decompressor");
 719 #endif